C3 – Improvement Recommended

C2 - Potentially Dangerous

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If you are completing an EICR (Electrical Installation Condition Report) under the 18th edition of the wiring regulations BS7671, then this category of fault C3 – Improvement Recommended is for any type of fault which does not preset any form of danger to the installation.

Therefore this classification code on EICRs is reserved for faults which are relatively minor.

Any fault which attracts this code will not affect the outcome of the report. There is no limit to how many C3 – Improvement Recommended code issues an installation can have and still be a satisfactory test.

Indeed, on commercial installations there can be thousands of these type of small faults

What Different Faults Are Considered C3 – Improvement Recommended?

This is really reserved for faults which are relatively minor when compared with C1 & C2 issues.

A brief run down of the sorts of things which would be classified as a C3 – Improvement Recommended issues under the 18th edition are:

  • Incorrect Labelling Of MCBs – This issue blights a huge percentage of installations throughout the UK with substandard labelling to indicate what a circuit is or does.
  • No RCD Test Labelling (where required) – Similar to above, there are a number of different labelling issues which fall under this category. If the installation has an RCD or RCBO, then it must have a test label fitted to the distribution board. This used to be that the RCD should be tested quarterly, but in an unusual relaxing of recommendations, under the 18th it is now to be tested every 6 months.
  • No BS7671 Dual Colour Label (where required) – If the installation has any wiring which is to the older BS7671 wiring colours, then a warning notice must be fitted. If the installation does have the older colour wiring, not having a label would be classed as C3 – improvement recommended. Newer (2004>) installations are to the harmonised colours and do not require a warning notice.
  • No ‘Safety Earth Connection’ Labels Fitted – There are a number of points throughout the installation where ‘Safety Earth Connection’ labels must be fitted (specifically to bonding connections & external earth terminals). If these labels are not fitted at the correct locations then this would be coded under this category.
C3 - Improvement Recommended - Provision Of Earthing/Bonding Labels At Appropriate Locations
C3 – Improvement Recommended – Provision Of Earthing/Bonding Labels

Inspection Schedule Tick Sheet Entries

If you are wondering what particular electrical inspections apply to C3 – Improvement Recommended issues mainly, then take a look at the list below. This is from an updated 18th edition inspection schedule. This particular schedule is for a domestic EICR, although broadly the same categories fit for any commercial EICR:

4.1 – Adequacy of working space/accessibility to consumer unit/distribution board

The consumer unit should be in an accessible location so that both the end user can access to reset, or it can be accessed to complete maintenance.

Furthermore, in commercial settings with multiple distribution boards and plant rooms, there are particular space requirements which must be adhered to regarding accessibility and working space.

Anything that does not have the room to open the front flap for example or at the back of a ridiculously tight kitchen cupboard, give it a C3.

4.2 – Security Of Fixing

The consumer unit must be adequately secured to prevent any movement or strain to connections. If the board is very slightly loose then this may fall under this category of fault. If there is any significant straining then this would be classed as a C2 – Potentially Dangerous

4.3 – Condition of Enclosure (IP rating) 

If the bottom or side of the consumer unit does not meet the IPx2 requirement, this is a C3 – improvement recommended issue. This is called the ‘finger test’ and is to ensure that a finger cannot be placed inside the consumer unit. There is a British standard mechanical ‘finger’ that is used to demonstrate this!

4.4 – Condition Of Enclsoure(s) in Terms Of Fire Rating 

Since 2015 with the introduction of amendment 3 to the 17th edition of the wiring regulations, it has been a requirement to fit ‘non-combustible’ enclosures in domestic properties.

If the consumer unit in a domestic house is not of a non-combustible type, and is located either on the SOLE escape route or underneath a wooden stairs would it deem to be a C3 – Improvement Recommended issue.

If the board is anywhere else then this does not require recording as a code. This is quite often used by unsruplulous electricians as a way to get people to upgrade consumer units to metal enclosures. I’ve even heard of the ’18th edition consumer unit’ (not exactly sure what that is?) when people are trying to strongarm homeowners into upgrading older boards.

However some of the boards they are telling customers need upgrading are like 5 years old! Nothing whatsoever wrong with them!

4.17 – Protection Against Electromagnetic Effects Where Cables Enter Consumer Unit/Enclosures

Whenever a cable is brought through the outer skin of a ferromagnetic enclosure (so any metal consumer unit/distribution board), it must pass all conductors through the same entrance to the enclosure. So both the Live & Neutral need to go through the same gland or bush.

Failure to do this builds up electromagnetic currents known as ‘eddy currents’ within the enclosure. This causes the piece of metal between the 2 glands/bushes to get hot.

In the case of domestic installations this would usually be the case with the meter tails having being brought through 2 different glands to a metal consumer unit. (alternatively, this has been seen with ring final circuits where each leg of the ring is brought through a different gland/bush/etc… In this instance then a C3 – Improvement Recommended is probably the most appropriate code, simply for the fact that the eddy currents produced are going to be minimal under domestic current draw conditions. However, any large commercial or industrial installations where you see this, particuarly with 3 phase, then a C2 – Potentially Dangerous is probably the more appropriate coding.

4.19 – RCD(s) Provided For Additional Protection/Requirements

There are a number of different inspections covering the more in-depth RCD requirements (such as provision for all sockets & cables buried less than 50mm). As such, this is more of a general look over the whole issue of no RCDs on the installation. When I am coding, if there any C2 issues for the more in depth RCD inspections further down, I apply them to that particular inspection. This one is generally a C3 – Improvement Recommended for installations which have split load boards and may have a small number not covered by their own RCD/RCBO.

C3 - Improvement Recommended - RCDs Provided For Additional Protection Requirements
C3 – Improvement Recommended – RCDs Provided For Additional Protection Requirements

5.1 – Identification Of Conductors

This covers the correct labelling/colouring requirements to identify what a conductor is.

5.2 – Cables Correctly Supported Throughout Their Run

The first thing to be aware of when considering this inspection on an EICR is that of limitations. By that I simply mean to need to be clear in the limitations section at the front of the EICR exactly what you are testing. You need to be clear to include everything, and then hence what you are not testing neither.

I’m not suggesting that you put silly limitations on a test in order to lower the workload, but there are a number of places you simply cannot check as part of an EICR. On a domestic EICR, there is no expectation that you will be lifting floorboards or chipping out walls to check the cables within. Commercial EICRs will have some similar limitation governed by what you cannot access.

However if you do see a cable which is not adequately supported, then this is definitely the place to record that. If the cable is left loose like the meter tails below, there is a chance that they could be snagged and pulled from the consumer unit or meter. However, we also know that the risk of this is pretty low and hence it’s only really a C3 – Improvement Recommended issue.

Obviously there will be occasions when this is more serious, cables outdoors and such like, and due consideration should be given to using a C2 – Potentially Dangerous code for those instances.

C3 – improvement recommended - meter tails service cable hung loose
C3 – Improvement Recommended – Meter Tails Not Adequately Supported

5.4.1 – To Include The Integrity Of Conduit & Trunking Systems (metallic & plastic)

This inspections centres around conduit systems containing non-sheathed cables.

Any lack of integrity of the conduit/trunking would have to recorded on the EICR. Assuming it does not expose no unsheathed cables which are accessible to touch, and assuming it poses no risk of damaging the cable insulation, then it would just be recorded as a C3 – Improvement Recommended issue.

Again, due consideration should be given to erring on the side of caution in these instances and considering a C2 – Potentially Dangerous issue:

  • Bare Unsheathed Cables are accessible to touch – In this instance then there is a particular danger of shock due to the less durable insulation as opposed to the more durable PVC outer sheath.
  • Cable Insulation/PVC sheath is in contact with sharp metallic edge – This presents a more serious risk of cable damage and hence must be coded accordingly
  • Corrosion of metallic trunking/conduit – This can cause a number of issues, one being the structural integrity, the other being sharp edges against cables and the third being loss of CPC connection in some instances (where the trunking/conduit is being used as a cpc/earth connection)

5.9 – Wiring System(s) Appropriate For The Type & Nature Of The Installation & External Influences

This particular inspection is yet another of those which has a ‘sliding scale’ of severity

One you will encounter most often if completing domestic EICRs is the use of T&E cable on exterior walls. T&E cable is not designed for use where it is subject to direct sunlight and weathering. This causes it to deteriorate over time, the severity of which depends on the level of exposure. If the outer skin of the cable has already cracked or looks like snakeskin then this would be a C2 – Potentially Dangerous issue.

However, if the cable is relatively new and shows no immediate signs of deterioration then a C3 – Improvement Recommended would be more appropriate.

Commercial considerations are slightly different: any cable which is subject to mechanical stresses, high temperatures or any other form of ‘external influence’ needs to be carefully considered and the appropriate cable used. There are instances where no danger may arise, however any inadequate specified cable which could pose a danger must be recorded as a C2.

5.10 – Concealed Cables Installed In Prescribed Zones

The first thing to be aware of when considering this inspection on an EICR is that of limitations. By that I simply mean to need to be clear in the limitations section at the front of the EICR exactly what you are testing. You need to be clear to include everything, and then hence what you are not testing neither.

And you are definitely not going to start chipping finished plaster walls to pieces to check this one. So lets be clear about it and record it in the limitations part of section 4 before we proceed further.

HOWEVER: During the course of the other inspections you are completing, it may become apparent that a cable is definitely not buried in the prescribed safe zones.

Again, I would debate that this is only a C3 – Improvement Recommended issue and nothing more serious. Particularly in the case of newer boards with RCD protection. That being said, there may be some circumstances where you may feel this warrants a more serious C2 code where there could be a particular risk of impact damage

5.12.1 – Provision Of RCD Protection For All Socket Outlets Of Rating 32A or Less

This inspection is one to check that each socket of less than 32A rating is provided with additional protection with an RCD not exceeding 30mA.

There are particular exemptions which can apply, where a documented risk assesment has taken place, which may mean that this issue does not even need coding.

However, in most instances, general 13A socket outlets need RCD protection, as do any 16A or 32A sockets (whether single or 3 phase).

As the more serious issue of no RCD protection for supplies to portable outdoor equipment would be a better place to consider a C2, we agree with the guidance set out in BPG4 – Electrical Safety First Best Practise Guide 4 – EICRs.

This basically states that, in general, sockets without RCD protection would be considered a C3 – Improvement Recommended. This is more serious and would be coded a C2 -Potentially Dangerous in instances where portable outdoor equipment could be used from that circuit.

From a domestic point of view, we would consider no RCD on upstairs sockets as a C3 – Improvement Recommended issue, whilst an outdoor socket with no RCD for additional protection would be more serious and hence a C2. Obviously the increased risk of a fatal shock whilst outside in contact with ‘true earth’ presents a much higher risk.

In this instance, a 4th storey flat is unlikely to be using their sockets to power a lawnmower. A socket outlet within a detached shed or garage on the other hand, may be a much higher risk of being used for something which may involve using power outdoors.

A commercial EICR will have to consider similar risks in the sense that certain sockets powering semi-permanent fixed equipment may not have a particularly high risk attached to it’s use. A socket outlet in a sports centre or even a medical centre has a completely different risk. (Certainly with regards medical properties as these have their own set of additional rules under the Special Locations sections)

Socket Circuits Protected by RCBOs. Note this method involves using a lot of separate RCBOs on larger installations. It does however, offer the greatest protection whilst maintaining ability to isolate faults so they don’t affect further circuits

5.12.3 – For Cables Concealed In Walls At A Depth Of Less Than 50mm

This is a particular inspection which has 2 strong opposing viewpoints. It doesn’t help that these opposing viewpoints are from the 2 main industry publications on EICR coding, this being the Best Practice Guide 4 & also NAPIT’s Codebreaker Book.

Both publications are from industry leading bodies and are both thorough and concise on their advice, written by experts in the field.

We choose to follow the advice set out in best practice guide 4, however that does not mean that I would necessarily argue that the advice from NAPIT is wrong. It’s just a different viewpoint.

The BPG4 guidance on this issue is that it is to be considered as a C3 – Improvement Recommended issue.

NAPIT’s Codebreaker book lists this issue as a C2 – Potentially Dangerous issue.

5.12.5 – Final Circuits Supplying Luminaires Within Domestic (Household) Premises

This is another disparity between BPG4 & the Codebreaker book.

Best Practise Guide 4 lists this as a C3 – Improvement Recommended issue.

Codebreaker lists this as a C2 issue, again erring on the side of caution.

This is a new regulation introduced as part of the 18th edition. The question that you have to ask yourself is does the circuit suddenly provide a potential danger (remember the meaning of those words, and look here if you need to check some of the things that are considered as potentially dangerous)

5.18 – Condition Of Accessories

If any switches/sockets or other accessories have any light cracks (and by light I mean hairline), but not as bad as missing pieces or any thermal damage.


  • There is much more information on what each exact inspection from the schedule entails by clicking on the links to each page.

Where possible there are pictures and diagrams, together with photos of things which might be encountered on that particular inspection.

Further Reading & Resources

There is further information available throughout the industry on what exactly a C3 – Improvement Recommended fault is and what it means to both electricians and end users of installations.

As our site is still in its infancy, this section is pretty limited at present. We endeavour to keep this section fresh and up to date (last updated October 2020)

  • Electrical Safety First : Best Practice Guide 4 EICR – This document contains some good information for free on the best classification codes to assign to a wide variety of issues. We base much of our inspection & testing ethos on the that found within this guide
  • NAPIT : Codebreakers – This is a printed book from the registration body NAPIT. It includes a very detailed set of tables containing lists of potential faults and classification code they recommend to assign. There has been a lot of debate throughout the electrical industry as of late with regards the somewhat more strict guidelines which the latest updated version of the book seem to offer.

5 Responses

  1. If you have a plastic consumer unit just inside your front door to your flat which is your only escape if there was a fire should a metal consumer unit be fitted. We are a block of 10 flats and electricians have different opinions and we have a mixed bag over the block. Please could you give advice.

    • Hello John, many apologies for the delayed response.

      I have heard this particular issue raised before. My personal thoughts are that the plastic board is fine, as long as it does not interfere with a communal means of escape. As long as it is just the single unit flat then I would consider this to just be a C3 – Improvement Recommended issue.

      Kind regards
      Electrical Assistance

  2. What are thoughts on a domestic premises ground floor lighting circuit with an external light fitting and RCD/RCBO protection. Does this fall into the same bracket as external socket or and externtion lead from a ground floor socket circuit as a code C2. Regardless of class 1 or 2 light fitting with CPC?

    kind Regards

    • Hello Ben, thanks for posting the question.

      To my mind, I would say no. A socket outlet could be powering anything, and the main problem which introduces the extra risk (which would warrant a C2 – Potentially Dangerous if it had no RCD) is that any trailing lead supplied by a socket could be damaged/cut and cause a serious shock in contact with “true” earth outdoors.

      In general, a light fitting would be ‘fixed’ and thus have a lower risk of damage to any cables which would cause a shock. A properly fitted & installed light class 2 light would have no chance of contact with live parts due to the double insulated nature. A class 1 light properly connected to a CPC should operate the protective device in the unlikely event that a wire comes loose.

      That being said: – An EICR conducted properly is a risk assessment exercise. Whilst any guide (such as BPG4 or codebreakers) can help, ultimately it is the inspecting electricians job to code appropriately to whatever risk may be necessary. If a class 1 light fitting is connected to a non RCD protected circuit and you feel this represents a higher risk for whatever reason, then you can certainly use whatever code you feel appropriate. One example may be metallic light fittings buried in the floor, in the example of street furniture.

      Hope that helps?
      Kind regards

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